Single-Tree Selection Silviculture Affects Cavity Resources in Mixed Deciduous Forests in Thailand

Abstract

Thailand's forest ecosystems contain a diverse vertebrate fauna and >30% of the species are thought to use cavities in trees. Forest management practices may significantly alter cavity availability for hole-nesting vertebrates. The effects of single-tree selection systems, commonly used in Thailand, on tree cavity abundance have not been extensively studied in any forest ecosystem, and no studies have been conducted in Thailand. We measured the effects of single-tree* selection harvest on cavity availability in mixed deciduous forests. We compared tree and cavity densities in unlogged and logged forests (5 stands in each type) in Huai Kha Khaeng Wildlife Sanctuary (HKKWS) in western Thailand. Tree densities (t = 2.89, 8 df, P = 0.02), cavity-tree densities (t = 4.27, 8 df, P = 0.003), and cavity densities (t = 4.44, 8 df, P = 0.004) were greater in unlogged than in logged stands. Ninety-two percent of cavity trees were alive; dead trees were uncommon, probably because of annual ground fires. Alangium salviifolium, Lagerstroemia spp., and Vitex spp. were the taxa most likely to form cavities, accounting for >30% of all trees and 66% of the cavities in unlogged habitats. Logging reduced tree densities of Vitex spp., but did not affect tree densities of Lagerstroemia spp. or A. salviifolium, nor cavity densities in Lagerstroemia spp. and Vitex spp. However, logging reduced cavity densities in A. salviifolium. Single-tree selection cutting reduced cavity abundances in these mixed deciduous forests. Maintenance of cavity-forming species and leaving more large-diameter trees may be required to maintain habitat for cavity-dependent wildlife.